What if you'd held BIIB?
A $1,000 investment in Biogen Inc. (BIIB) at the month-end close of 2019-03 would be worth $985 at the close on 2026-10-16: a -1.5% price return. Through September 2026, the latest month the fund has reported, the same $1,000 became $957 in BIIB and $3,022 in an S&P 500 index fund (TSP C Fund). The fund figure includes reinvested dividends; the stock figure does not, so the comparison favors the fund.
Your scenario
Result
If you'd bought $1,000 at the start of each year
Value of $1,000 invested on January 1 of each year and held to the latest close. Click any year for the full story.
Every year, $1,000 from 2019
| Year | Value of $1,000 | Year return |
|---|---|---|
| 2019 | $1,000 | — |
| 2020 | $826 | -17.4% |
| 2021 | $809 | -2.0% |
| 2022 | $933 | +15.4% |
| 2023 | $873 | -6.5% |
| 2024 | $515 | -40.9% |
| 2025 | $593 | +15.0% |
| 2026 | $785 | +32.3% |
Best and worst month to buy
The best month to have bought BIIB was 2025-04, at a close of $121: $1,000 then is $1,923 today. The worst was 2021-06, at $347: $1,000 then is $672.
FAQ
What would $1,000 in BIIB be worth today?
About $985 at the latest close, a price return of -1.5%. That is $1,000 put into BIIB at the 2019-03 month-end close, the first in this price history.
What were the best and worst years for BIIB?
BIIB's best calendar year since 2019 was 2026 (year to date), with a +32.3% return: $1,000 invested at the start of that year became about $1,323. Its worst year was 2024, at -40.9%.
Does the calculator include dividends and splits?
Splits only. Price return: adjusted for stock splits, dividends not included. Prices are split-adjusted automatically; a ticker whose history we could not adjust with confidence starts later or is not shown.
How much would $100 per month in BIIB have grown?
To about $9,748 from $9,200 invested, putting in $100 at every monthly close since 2019-03.
Did BIIB beat the S&P 500?
No. From the March 2019 month-end through September 2026, BIIB trailed an S&P 500 index fund by 68.3%: $1,000 in the fund (the TSP C Fund, dividends included) became $3,022, and $1,000 in BIIB (price only) became $957. The fund's monthly returns are published at tsp.gov.
Is this investment advice?
No. Wall Street Regrets is an entertainment and education tool. Every number here is a historical calculation, and past performance never guarantees future results.
Methodology
The figures on this page use BIIB's historical price data from 2019-03 to 2026-10. The tables and the calculator above use month-end closes.
Prices come from IEX Historical Data. A "year" scenario invests $1,000 at the prior December's month-end close and values it at the latest close. Amounts in other currencies are converted at month-end exchange rates published by the European Central Bank and, for earlier years, the Federal Reserve: into US dollars at the buy date's rate and back at the sell date's rate, so the return includes the currency move.
Prices are the last regular-session trade on IEX (Investors Exchange) each day, which can differ slightly from the official close. Month-end closes miss the highs and lows inside a month. Figures ignore taxes, fees and the currency effects of non-USD listings.
What if you'd held…
Prices as of the last IEX trade on 2026-10-16. Data delayed end-of-day.